There is a growing demand in recent years for miniature-sized image pickup devices provided with wide-angle lenses capable of taking images in wide angles for use in portable phones and the like apparatuses equipped with cameras. One of such image pickup devices comprises, for instance, an image pickup lens housed in a holder with a cylindrical lens barrel, and an image sensor having a photoreceptor in the center and placed in a position of a predetermined distance with respect to the image pickup lens. The image pickup lens housed in the holder generally comprises a plurality of lenses. A rear lens located nearest to the image sensor (i.e., image-forming plane) is the largest in size among the plurality of lenses, and the rear lens is fixed by adhesion to the lens barrel of a size larger than an outer dimension of the rear lens.
A conventional art disclosed in Patent Literature 1 is one of the examples as known to be relevant to the structure of fixing a rear lens to a lens barrel by adhesion with consideration given to downsizing. Patent Literature 1 discloses a structure comprising a lens barrel provided with a ventilable slit opening (i.e., an aperture formed by cutting out a part of a peripheral edge of an image pickup lens (and a light shield) housed in the lens barrel), and a side surface of the rear lens is fixed by bonding to an end surface at an insertion side of the lens barrel while sucking the rear lens through the slit opening, for instance.
In the case of the image pickup device described in Patent Literature 1, however, there exists a problem of conflicting with downsizing since the lens barrel has an outer dimension larger than the largest external dimension of the rear lens that inevitably increases the size of the image pickup device with that of the lens barrel.
There is also a possibility that an adhesive material sticks to surfaces of other lenses housed in the lens barrel or gets into a space between the lenses in the process of fixing the side surface of the rear lens to the end surface at the insertion side of the lens barrel while sucking the rear lens. This results in other problems such as an increase in the possibility of forming ghost images (i.e., a phenomenon of admitting incident light blurred) attributed to the lens surface or degradation of resolution due to shifting of the optical axis of the lenses.